Ethanol Enhances Astaxanthin Production by Aurantiochytrium sp. O5-1-1

Two-percent ethanol increased the astaxanthin productivity of heterotrophic microalgae Aurantiochytrium sp. O5-1-1 to 2.231 mg/L, 45-fold higher than under ethanol-free condition. Ethanol in the medium decreased at the same rate as spontaneous volatilization, suggesting that it was not a transient signaling factor but a continuous stress on the cells. The triply mutated strain OM3-3 produced 5.075 mg/L astaxanthin under 2% ethanol conditions. Furthermore, the astaxanthin accumulation of the mutant OM3-9 was 0.895 mg/g, which was 150-fold higher than that of strain O5-1-1 in ethanol-free condition. These results are beneficial for the commercial exploitation of carotenoids producing Aurantiochytrium spp.